fn main() {
    println!("Hello, world!");
}
fn gcd(mut n : u64, mut m: u64) -> u64{
    assert!(n!=0&&m!=0)
    while m!=0{
        if m<n{
            let t=m;
            m=n;
            n=t;
        }
        m=m%n;
    }
    n
}
